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2011 Assessment of BRB -5 for Compliance with Phase ill Performance Standards <br />COVER <br />As described above, sample adequacy based on first -hit values was achieved for BRB -5 and the <br />Sagebrush Reference Area, but it was not for the Mountain Brush Reference Area. Thus, in consideration <br />of the lack of a sample size sufficient to detect a 10 percent reduction in the mean with 90 percent <br />confidence (i.e. sample adequacy), the upper limit of the possible values of the true mean (with a sample <br />size of 21) was determined. This can be done in either of two ways. <br />1) Confidence Intervals <br />C.I. = =t =921 =1.725 =3.44 <br />20.95 + 3.44 = 24.39 <br />2) Sample Adequacy Expression <br />s2t2 <br />N = d 2 .T2 <br />jX_ 2t2 9.152 :1.7252 <br />d= _ <br />2 N J. 20.952 :2i <br />= 0.1644 <br />T + d = 20.95 + (20.95 * 0.1644) = 24.39 <br />24.39 percent allowable herbaceous cover represents the highest possible value of the true mean for the <br />Mountain Brush Reference Area. <br />[Note in the above two- tailed t values with n -1 degrees of freedom are used. We are concerning <br />ourselves with the full range of possible values for mean, thus bi- directional concerns are evident. From <br />the CDRMS point of view this pushes the limits out further and produces the highest maximum value for <br />the mean (at 90% confidence). Also note that as sample size proceeds past the minimum (15) samples, <br />the upper confidence limit is likely to decline if only because n increases in the denominator of expression <br />1) above. Thus use of the upper confidence limit as the cover value for the Mountain Brush Reference <br />Area likewise takes the highest value forward into hypothesis testing and thus protects the interests of <br />CRDMSJ <br />iL01 <br />